From 3d435cc9688b36ef887d9210bb0dd2f0eaab7750 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi.kivity@gmail.com>
Date: Wed, 2 Jan 2013 20:42:10 +0200
Subject: [PATCH] mutex: add with_lock() function
This function allows executing a block of code under a lock, with a guarantee
that any exit from the block will release the lock.
Examples:
with_lock(my_mutex, [&] { a += b; });
return with_lock(my_spinlock, [&] {
return my_list.size();
});
---
libc/fd.cc | 21 +++++++++++----------
mutex.hh | 9 +++++++++
2 files changed, 20 insertions(+), 10 deletions(-)
diff --git a/libc/fd.cc b/libc/fd.cc
index 75c19c73b..6b3741ada 100644
--- a/libc/fd.cc
+++ b/libc/fd.cc
@@ -40,14 +40,15 @@ int open(const char* fname, int mode, ...)
}
auto desc = std::shared_ptr<file_desc>(
new file_desc(f, mode & O_RDONLY, mode & O_WRONLY));
- std::lock_guard<mutex> guard(file_table_mutex);
- auto p = std::find(file_table.begin(), file_table.end(),
- std::shared_ptr<file_desc>());
- if (p == file_table.end()) {
- file_table.push_back(desc);
- p = file_table.end() - 1;
- } else {
- *p = desc;
- }
- return p - file_table.begin();
+ return with_lock(file_table_mutex, [&] {
+ auto p = std::find(file_table.begin(), file_table.end(),
+ std::shared_ptr<file_desc>());
+ if (p == file_table.end()) {
+ file_table.push_back(desc);
+ p = file_table.end() - 1;
+ } else {
+ *p = desc;
+ }
+ return p - file_table.begin();
+ });
}
diff --git a/mutex.hh b/mutex.hh
index f28027602..4b3a1ab9d 100644
--- a/mutex.hh
+++ b/mutex.hh
@@ -1,6 +1,8 @@
#ifndef MUTEX_HH
#define MUTEX_HH
+#include <mutex>
+
class mutex {
public:
void lock();
@@ -8,4 +10,11 @@ public:
void unlock();
};
+template <class Lock, class Func>
+auto with_lock(Lock& lock, Func func) -> decltype(func())
+{
+ std::lock_guard<Lock> guard(lock);
+ return func();
+}
+
#endif
--
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